Surveying methods and apparatus

ABSTRACT

The invention relates to a surveying system, comprising at least one total station unit ( 210, 220 ), and at least one target ( 201, 203 ), said targets having wireless communication means, each unit provided with a unique wireless communication address for wireless communication, the wireless communication to be used to activate a selected total station ( 210, 220 ) to identify and measure the location of a chosen target ( 201, 203 ) in relation to a relative reference system, each target having identification means to be used by the total station for identification of the chosen target, each total station having identifying means used for identification of the chosen target to be measured. The invention also relates to a target and a method for surveying using the total stations and the targets according to the system.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation-in-part of co-pending International ApplicationPCT/SE2003/002028, with an international filing date of 19 Dec. 2003 anddesignating the United States of America, the content of which isincorporated herein by this reference. Priority benefit under 35 USC 119is claimed of patent application number 0203830-5 filed in Sweden on 20Dec. 2002, the content of which is incorporated herein by thisreference.

FIELD OF THE INVENTION

The present invention generally relates to surveying and morespecifically to a surveying system including several surveying units forsurveying and equipment such as targets, radio receivers and methods andmeans for co-operation between such units.

BACKGROUND OF THE INVENTION

The art of surveying involves the determination of unknown positions orsetting out of known coordinates using angle and distance measurementstaken from one or more known positions. In order to make thesemeasurements a surveying device frequently used is a total station. Thedevice is generally operated by two users, one user pointing the totalstation at a target held by a second user.

The user traditionally makes the pointing optically, using a telescope.Robotic total stations have been developed which assist the user inlocating the target and aligning to it. The robotic total stationsinclude servomotors that allow the apparatus to be rotated toautomatically align the station with the target. The automatic alignmentcan be done either against the reflector used for distance measurement,in which case a separate light (IR or visible) beam is sent from therobotic total station and reflected back from the reflector, or thetarget may be equipped with a light source.

In both cases the total station is equipped with an optical receiver toreceive the alignment signal reflected from the reflector or transmittedfrom the light source, to be processed and used to automatically alignthe total station against the target. A system using both possibilitiesis disclosed in EP 0 465 584.

These robotic total stations can automatically find a target, lock to itand follow the target if it is moved. There are a number of differentmethods used to enable the total station to find a target. Normallythese methods include scanning a certain “window” or angle, and lockingon any target within the window.

With this type of more complex total station the user may be only oneperson and he is then normally working at the target in order to choosethe point to be measured or mark the point to be set out. By givingcommands via a radio link the user can make the station search for thetarget and lock to it. When the user once has marked all points to bemarked on the site which are accessible for the total station, the totalstation has to be moved to a new location in order to measure furtherpoints on the site.

To move the total station requires not only the physical movement of theapparatus, but also, every time the station is moved, the exact locationand orientation of the station has to be determined anew. Themeasurements have to be exact in order to correlate the new measurementsto the earlier by establishing the location and the orientation of thestation in relation to known reference points. Understandably this takestime, typically 30 minutes or more, and the users dependent on the totalstation for staking out will then have to wait, not only for the stationto be moved, but also for the location and direction to be establishedin the new position.

This need of relocation of the total station arises on large sites to besurveyed for different reasons, e.g. the direct line of sight isobstructed by a building or a mound, or the like, or when doingsurveying work for constructions of roads or runways etc. where the worksite covers extensive stretches of land.

However on large building sites, more than one measuring crew may beworking in the same area. This means there is a risk of a total stationlocking on the wrong target.

One way of aiding a total station to quickly find a target (e.g., reducescanning time or need for scanning) is described in U.S. Pat. No.6,035,254 wherein a surveying system using a navigation GPS receiver atthe target for determination of the coarse position of the target isdescribed. The target thereafter transmits to a total station positioninformation estimating location of the target. The total station is thenaligned coarsely with the target and can lock on it.

The prior art does not address the problem of selecting a specifictarget among several possible targets, when the targets appear to beclosely located as viewed from the total station. A further problem isencountered when several targets and several total stations are locatedon the same general site; the problem of unique identification of allelements in the survey for proper linking of target with total stationis further compounded when there are different users in the same generalsite.

SUMMARY OF THE INVENTION

For the purpose of this description and claims the following expressionsare to be understood as follows:

-   -   Identification means are means that identify in a chosen manner        a target to any other member of the system.    -   Identifying means are means being part of the total station for        identification of a specific target.        Unique wireless communication address for each unit is the        address used in wireless communication between different units        during measurements, i.e. target, total station, memory device.        The unique address may also be used in registering the gathered        measurements.

Embodiments in accordance with the invention have one or moreadvantages, such as

-   -   1. enabling interaction between total stations and targets,    -   2. enabling a total station to lock on a specific target making        certain that it is the intended target.    -   3. allowing a target to ask for assistance, i.e., having a        specific total station locking on it.    -   4. having the position of any one target in the system measured        by more than one total station,    -   5. allowing use of a common target for several measurements,    -   6. facilitating selection of one target among several, when the        separation of the targets is large enough to exclude unwanted        targets,    -   7. enabling increased accuracy of the measurements,    -   8. providing a greater radio range and better transfer of data.

Embodiments in accordance with the present invention provide systems andmethods for determining positions, comprising one or more totalstation(s) and one or more target(s), wherein each unit comprises a twoway wireless data communication device to be able to communicate withall possible units in the system in a radio net, each unit having aunique address to be used to enable exchange of commands or data betweencertain units.

Embodiments of a surveying system in accordance with the inventioncomprise at least one total station unit, and at least one target unit,said units having wireless communication system means, each unitprovided with a unique address for wireless communication, the wirelesscommunication usable for activating a selected total station to identifyand measure the location of a chosen target, each target havingidentification means used by the total station for identification of thechosen target, each total station having identifier means used foridentification the chosen target to be measured.

The location may according to embodiments of the invention be measuredin relation to a relative reference system.

A system according to embodiments of the invention may further haveidentification means of each target in the system comprising a modulatedlight source, each of the targets exhibiting different modulationschemes for the respective light sources, the identification being theselected modulation scheme.

Further in accordance with embodiments of the invention the systemidentification means of each target in the system may comprise a lightsource of which the modulation scheme may be set from measurement tomeasurement such as to give the light sources of targets close to eachother different modulation schemes, the identification being theselected modulation scheme.

Further in accordance with embodiments of the invention theidentification means of each target in the system may comprise asatellite-positioning system receiver, the identification being theapproximate location given by the positioning system.

Further in accordance with embodiments of the invention each target isprovided with wireless communication means, and a unique wirelesscommunication address for wireless communication, the wirelesscommunication to be used to activate a selected total station toidentify and measure the location of the target in relation to arelative reference system, the target having identification means to beused by the total station for identification of the chosen target.

Further in accordance with embodiments of the invention theidentification means of the target may comprise a modulated lightsource, the target exhibiting different modulation schemes for the lightsources, the identification being the selected modulation schemes.

Further in accordance with embodiments of the invention theidentification means of the target may comprise a light source of whichthe modulation scheme may be selected from measurement to measurement,the identification being the selected modulation scheme.

Further in accordance with embodiments of the invention theidentification means of the target may comprise a satellite-positioningsystem receiver, the identification being the approximate location givenby the positioning system.

Further in accordance with embodiments of the invention methods areprovided comprising the following steps:

-   at least one total station is positioned and aligned in a given    co-ordinate system;-   a target, the position of which is to be measured, exhibiting    identification means which are exchanged with a chosen total station    of the at least one total stations;-   the total station set up to search for said target, using the    identification means to identify that the total station is aligned    with said target for measurements;-   measurements of the location of said target performed by the total    station.

In accordance with embodiments of the invention the measurement data maybe sent by wireless communication to a memory means.

In accordance with embodiments of the invention the identification meansmay comprise a modulated light source, the modulation scheme for thelight sources being unique to the target, the identification being theselected modulation scheme.

In accordance with embodiments of the invention the identification meansmay comprise a light source of which the modulation scheme may be setfrom measurement to measurement, the identification being the selectedmodulation scheme.

In accordance with embodiments of the invention the identification meansmay comprise a satellite-positioning system receiver, the identificationbeing the approximate location given by the positioning system.

Embodiments of a target in accordance with the invention comprise areflector to be used as a target for the distance meter in the totalstation, a means for enabling the robotic total station to lock on thetarget, and an identification means, which positively identifies thetarget to the total station to lock unto the identified target. Theidentification means at the target may e.g. be either a modulated lightsource using a selectable modulation scheme, or a GPS receiver todetermine the coarse position of the target, the identifying parameterin the first case being the selected modulation scheme and in the secondcase the coarse position. This identification means is used to enableany total station to determine that a specific target has beenidentified before locking on it.

The means at the target for enabling the station to lock onto the targetmay be the reflector itself or an additional means, e.g., a lightsource. This second light source may be identical to the identificationmeans, also when that is a modulated light source.

Embodiments in accordance with the present invention also provide aunique address for all units in the system to be used in a radiocommunication net, enabling each unit to select one specific unit for aspecific communication.

In embodiments according to invention the identification of a certaintarget is achieved using a modulated light source, as the identificationmeans on the target, where the modulation scheme (e.g. the modulationfrequency) can be changed. Any of a number of predeterminedcharacteristics can be activated by the operator or by a command fromone of the other units in the system. The total station can use thisspecific modulation scheme in different ways.

The total station may in one embodiment identify the specific modulation“on the run” when scanning for the target, and thus neglect all othertargets and when the selected target has been identified the station isallowed to lock to the specific target.

The total station may in a second embodiment first lock to a target,during the search procedure for a specific target, and then check themodulation scheme to establish if the actual target locked to was theintended one.

Choosing a specified modulation scheme for a target and giving order toa certain total station to lock to a target using that specific schemethus achieves the locking of a certain total station to a specifictarget.

In a further embodiment the specific target may, as is already knownwithin the art, comprise a GPS-receiver at the target for determiningits position. The identification means of the selected target will inthis embodiment consist of the position given by the GPS-receiver. Thisinformation may be translated to a specific total station via the radiocommunication (wireless link) provided, using the unique address of thespecific total station. The total station may then, using the translatedpositional data, align with the actual target and lock to it.

In a survey where several robotic total stations are used, the user ispreferably working at the target. The means for radio communication willthen enable the user to select one or more of the possible totalstations to lock on the specific target and to measure the locationthereof.

This provides the possibility of multiple measurements of the sametarget using different total stations providing more exact assessment ofthe location of the specific target.

Providing the targets with a specific identification means, e.g. aspecific modulation scheme also allows more than one user to use thesame target on a location and discriminate it from other targets. Thiscommon specific target may be a target used as a reference target on thelocation.

Using more than one total station also provides for savings in time inthat e.g. in the staking for a road one station may be moved andrealigned and the position thereof be ascertained while the surveyor/skeep on measuring and staking out points using another total station.

By providing wireless data communication in each unit the possibility ispresent to relay data between several units such as to extend the rangeof the communication. This also provides the possibility of gatheringall data at a common means for storing the data, such that there will beno need in downloading data from each unit separately, thus saving timeand also security in that the data will be available at the common datastorage and also in the individual total stations or the control unitsat the targets.

The communication will also facilitate for the different units to haveaccess to a common database containing construction data to be used forthe survey.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other advantages and features of the present invention will bemore readily understood from the following detailed description of thepreferred embodiments thereof, when considered in conjunction with thedrawings, in which like reference numerals indicate identical structuresthroughout the several views, and wherein:

FIG. 1 is a schematic illustration of a preferred embodiment of a systemaccording to the invention.

FIG. 2 is a schematic illustration of a method of using the system inconnection with road construction or the like.

FIG. 3 is a schematic illustration of a method of using the system at asite where moving construction machines are used.

FIG. 4 shows a flowchart of the operation of a system according to theinvention.

FIG. 5 is a schematic block diagram of a surveying target in accordancewith the invention.

FIG. 6 is a schematic block diagram of a robotic total station inaccordance with the invention.

FIG. 7 is a schematic diagram of a surveying system in accordance withthe invention.

FIG. 8 is a flow diagram illustrating surveying methods in accordancewith the invention.

DETAILED DESCRIPTION

In a preferred embodiment of the invention, several total stations andtargets interact as is shown in the schematic drawing in FIG. 1. Threetotal stations 110, 120, 130 are shown, each having arrangements 111,121, 131 for sending out measuring beams for distance and alignmentmeasurements, and beams, and sensor arrangements 112, 122, 132 forreceiving the reflected or the transmitted beams from a target.

The sensor for receiving the alignment beam may be adapted to receivethe beam from an identification unit at the target, or a separate sensormay be used for detection of this identification. Optical alignmentmeans (telescope) may be arranged in order to align the total station(s)with any known point (not shown). Also provided are units for two-waywireless data communication, 113, 123, and 133, respectively.

The two-way wireless data communication may be of the cellular type,e.g. AMPS, PCS (Personal Communication Service) CDPD (Cellular DigitalPacket Data), and GSM using e.g. GPRS (General Packet Radio Service).For these systems the rule is that there must be at least one basestation to forward the data information. In areas where this type ofservice is not provided, e.g., Bluetooth® or Wi-Fi (Wireless Fidelity)may be used or a radio communication system specially for the systemdevised.

Also shown are targets 150, and 160, each target comprising a reflector(not shown) having units 152 and 162, respectively, for two way wirelessdata communication and units 154 and 164 for identification of thetarget.

In this preferred embodiment the identification units are light sourceswhich may be modulated using different selectable modulation schemes.The target may also comprises a control unit (not shown) including akeyboard, a display and a controller to manage the tasks entered via thekeyboard and to control the different units. The double-headed arrows140 indicate both the respective data communication and measuringpossibilities within the system. The system may be further provided witha memory means 170, for downloading of measurement data from the totalstations and the system may also be provided with suitable maps etc. forthe surveying work to be done, which may be stored in the memory means.The memory means is normally provided in the total station and thecontrol units at the targets but may be provided in a separate computerof e.g. the type PC.

When using the system, the user is preferably stationed at one of thetargets 150, or 160. The user sends a command using the unique addressto the appropriate total station, to align with the target having theappropriate modulation scheme and measures the distance and angles fromthe total station to that target, as is known within the art. Thesemeasurement data are then stored either locally in the total station, orsent via radio to and stored in the control unit at the target or in thecentral memory means, which are arranged to be addressable by all units(total station and targets) in the system. A second user at target 160can simultaneously use any non-occupied total station to align to thistarget and perform corresponding measurements. It has to be understoodthat a unit occupied with one measuring task will give a notice to anyuser trying to contact it indicating that it is not available for newtask until the first is finished. It is also possible to give usersdifferent priorities when asking for service.

An advantage when using this embodiment is that the total stations maybe set up in advance in locations on the site, which locations arewithin measuring distance (line of sight undisturbed) from all possiblemeasurement points on the site, or that at least one total station willbe within measuring distance from any chosen point. The user may thenchoose the appropriate total station(s) to perform the measurement(s).To be taken into account in this instance is the relative distance tothe total station chosen and also the relative locations of the chosenstations(s) i.e. two targets may be too close to each other seen fromone total station, but not from another total station. Having more thanone total station perform the measurement will ascertain a higherprecision overall for the data.

It is not certain that all points on a site will be within line of sightfor all of the total stations, the site may be a building site wherebuildings are erected and which will obstruct the view in somedirections. The site may also be of an undulating type, the grounditself obstructing the view.

In a second embodiment the identification units 154 and 164 at thetarget comprises GPS receivers. The identification is then performed bydetermination of the coarse position (in the range up to a few meters)of the target. Instead of transferring the modulation command to thetotal station as in the preferred embodiment the coarse position data isinstead transferred, and by calculating the approximate direction to thetarget, the total station can find it and lock to it, provided there isno other target close to the same direction.

In FIG. 2 a road construction site is shown, it may as well be arailroad or a run-way. In the drawing is shown three targets 201, 202,and 203 for setting out the edges of the roadway.

Shown are also two total stations 210, 220. The measurements areinitiated in the same manner as in the previous embodiment. Themeasurement relative to target 201, 202, and 203 are performed in afirst round. The bi-directional wireless communication paths 241, aswell as the bi-directional measurement beams 240 are both shown.

The method of locking both total stations 210 and 220 on the same target(in this case 202), can serve either as a check that there is nomismatch between the two total stations e.g. the locations andorientations are correct, or data from both stations can be used to geta higher accuracy of the measurement by averaging the measured positionof 202.

It is also apparent that, due to the unique address of every unit, itwill be possible to transfer data via radio from station 210 to station220 even if the radio range is not long enough to do that directly.

There may of course be several more targets, which are within line ofsight from the total stations 210 and 220. When all measurements to beperformed by the total station 210 has been made, this station isrelocated to a new place as indicated in the drawing by the totalstation 210′ and the dashed arrow 270. Also the target 201 istransferred to a new location indicated by 201′.

The manner in which the measurement data are stored and collected is thesame as the embodiment shown in FIG. 1.

The advantage of working in this manner is quite clearly that it is atime-saving measure to be able to relocate one total station includingthe determination and check of the exact new location of the station andthe alignment, while work is still going on using the other station(s).

A further advantage of the systems according to the invention is that ifthere are more than one team at a construction site e.g. they may usethe other teams units as each unit has a unique address.

In FIG. 3 a site similar to that in FIG. 2 but having a working machine,e.g. a grader 304 is shown. The working machine has a target/reflector303 for measuring the location of the working machine. There are twototal stations provided 310 and 320, both having measurement means andalso radio means for communication between the units of the system. Thesystem shown further comprises two targets 301 and 302 also providedwith means for wireless communication and for performing measurements.

The bi-directional wireless communication paths 341 are indicated, asalso the bi-directional measurement beams 340.

One or more of the total stations 310, 320 can be used to lock to thetarget on the machine 303 to guide the machine and control the workingpart of the machine via the radio link. More sensors can be provided onthe machine to determine the position of the working blade in a sitecoordinate system to facilitate an exact control of the work done by themachine. As the machine proceeds along the road the tracking has to betaken over by the next total station (320). When this is achieved thefirst station can be moved to a new location along the road (indicatedas 310′), without any interruption for the machine to wait for thetransfer. Again using a second (302) common target for two stations, acheck of the consistency of the new location and orientation can bedone.

Referring to FIG. 4, a preferred method of using the system in FIG. 1according to the invention may be as follows:

-   Step 1: Positioning and alignment of one or more total station(s)    with respect to two or more reference points is performed.-   Step 2: The user positions a target at a point to be measured.-   Step 3: The user chooses a modulation scheme to characterise the    target.-   Step 4: The user sends a command to the appropriate total station to    search for and lock to the target using the selected modulation    scheme.-   Step 5: The total station finds the target and locks to it. Lock is    indicated on the display at the target. Information may be forwarded    to the target via wireless communication or it may be stored in a    suitable memory means.-   Step 6: The user sends a command to the total station to measure the    position of the target.-   Step 7: The measured coordinates for the target location are    forwarded to the target from the chosen total station and on the    display of the control unit.-   Step 8: The user stores the coordinate data locally in the control    means of the target. Storing of measurement data in a common memory    means by transmitting data using radio means can also be performed.-   Step 9: Loss of target and choice of total station for new    measurements are taken as in step 4.-   Step 10: If further measurements needed, the procedure is repeated    from step 6.

In the target may also be provided a transponder adapted to react on atransmitted electromagnetic beam, from the total station as theidentification means. The transponder will then react and transmit thesignal back and possibly add a modulation to the signal.

Embodiments in accordance with the invention can include one or more ofthe following:

-   -   1. A surveying system, comprising at least one total station        unit (110, 121, 131; 210, 220; 310, 320), and at least one        target (150, 160; 201, 203; 310, 320) said target having        wireless communication means (152, 162), each target provided        with a unique address for wireless communication, the wireless        communication usable for activating a selected total station        (110, 121, 131; 210, 220; 310, 320) to identify and measure the        location of a chosen target (150, 160; 201, 203; 301, 303), each        target (150, 160; 201, 203; 301, 303) having identification        means used by the total station for identification of the chosen        target, each total station (110, 121, 131; 210, 220; 310, 320)        having identifying means used for identification of the chosen        target to be measured.    -   2. A system according to 1 characterized in that the location is        measured in relation to a relative reference system.    -   3. A system according to 1 or 2 characterized in that the        identification means (154, 164) of each target in the system        comprises a modulated light source, each of the targets        exhibiting different modulation schemes for the respective light        sources, the identification being the selected modulation        scheme.    -   4. A system according to any of the preceding characterized in        that identification means of each target in the system comprises        a light source of which the modulation scheme may be set from        measurement to measurement such as to give the light sources of        targets close to each other different modulation schemes, the        identification being the selected modulation scheme.    -   5. A system according to any of the preceding characterized in        that identification means of each target in the system comprises        a satellite-positioning system receiver, the identification        being the approximate location given by the positioning system.    -   6. A system according to any of the preceding characterized in        that memory means are provided for storing of measurement data.    -   7. A target to be used in a system according to any of 1-6, in        which said target is provided with wireless communication means,        and a unique wireless communication address for wireless        communication, the wireless communication to be used to activate        a selected total station to identify and measure the location of        the target in relation to a relative reference system, the        target having identification means to be used by the total        station for identification of the chosen target.    -   8. A target according to 7 in which the identification means of        the target comprises a modulated light source, the target        exhibiting different modulation schemes for the light sources,        the identification being the selected modulation schemes.    -   9. A target according to 7 in which the identification means of        the target comprises a light source of which the modulation        scheme may be selected from measurement to measurement, the        identification being the selected modulation scheme.    -   10. A target according to 7 in which in that identification        means of the target comprises a satellite-positioning system        receiver, the identification being the approximate location        given by the positioning system.    -   11. A method of surveying characterized by the following steps:        -   at least one total station is positioned and aligned in a            given co-ordinate system;        -   a target, the position of which is to be measured,            exhibiting identification means which are exchanged with a            chosen total station of the at least one total stations;        -   the total station set up to search for said target, using            the identification means to identify that the total station            is aligned with said target for measurements;        -   measurements of the location of said target performed by the            total station.    -   12. A method according to 11 in which the measurement data sent        by wireless communication to a memory means (170).    -   13. A method according to 9-12 in which the identification means        comprises a modulated light source, the modulation scheme for        the light sources being unique to the target, the identification        being the selected modulation scheme.    -   14. A method according to 11-12 in which the identification        means comprises a light source of which the modulation scheme        may be set from measurement to measurement, the identification        being the selected modulation scheme.    -   15. A method according to 10-11 in which the identification        means comprises a satellite-positioning system receiver, the        identification being the approximate location given by the        positioning system.

FIG. 5 is a schematic block diagram showing an active surveying target500 in accordance with embodiments of the invention. The target includesa reflector on a pole 505 as is conventional for passive surveyingtargets. The target further includes a controller 510 having a datastore 515 and input/output devices 520 such as a keypad for receivingcommands from a human operator and a display panel for displayinginformation to be viewed by a human operator. A wireless communicationunit 525 having an address 530 communicates with controller 510 forsending and receiving data by wireless communication. Address 530 ispreferably a unique address allowing communications from target 500 tobe recognized as coming from it and allowing communications to beaddressed to it.

An identification unit 535 in communication with controller 510 enablesa total station to identify target 500. Identification unit 535 can beimplemented as (1) a light source such as a laser source which emitslight modulated to indicate the identity of the target, (2) a lightsource such as a laser source which emits a light of a frequency whichindicates the identity of the target, and/or (3) a global positioningsystem receiver to determine and supply an approximate location of thetarget which indicates the identity of the target. In the case of aglobal positioning system receiver, the approximate location can betransmitted via modulated light such as a laser and/or via wirelesscommunication. The information which indicates identity of the target,such as the modulation scheme or frequency of the light source, canoptionally be modified by command from the controller so that targetswhich are located in close proximity to one another are assured of beingdistinguished from one another by a total station attempting to seek andidentify a specific target.

FIG. 6 is a schematic block diagram of a robotic total station 600 inaccordance with the invention. Conventional elements of a robotic totalstation 600 indicated collectively at 605 include a telescope, drivemotors for aiming the telescope, angle sensors for detecting azimuth andelevation of the telescope and a distance-measuring unit for measuringdistance to a target. In accordance with the invention, robotic totalstation 600 further includes a controller 610 having a data store 615and input/output devices 620 such as a keypad for receiving commandsfrom a human operator and a display panel for displaying information tobe viewed by a human operator. A wireless communication unit 625 havingan address 630 communicates with controller 610 for sending andreceiving data by wireless communication. Address 630 is preferably aunique address allowing communications from robotic total station 600 berecognized as coming from it and allowing communications to be addressedto it.

An identifying unit 635 in communication with controller 510 enablestotal station 600 to identify a target such as target 500 from a signalreceived from the target, generated for example by (1) a light sourcesuch as a laser source which emits light modulated to indicate theidentity of the target, (2) a light source such as a laser source whichemits a light of a frequency which indicates the identity of the target,and/or (3) a global positioning system receiver at the target todetermine and supply an approximate location of the target whichindicates the identity of the target. In the case of a globalpositioning system receiver, the approximate location can be receivedvia modulated light such as a laser and/or via wireless communication.

FIG. 7 is a schematic diagram of a surveying system in accordance withan embodiment of the invention. One or more targets 702, 712, 722 suchas target 500 and one or more robotic total stations 732, 742 such asrobotic total station 600 are located in a region to be surveyed. Thenumber of targets and total stations can be greater or fewer as neededfor the surveying task. Target 712 has a controller 704, a wirelesscommunication unit 706 and an identification unit 708; target 712 has acontroller 714, a wireless communication unit 716 and an identificationunit 718; target 722 has a controller 724, a wireless communication unit726 and an identification unit 728. Wireless communication messages canbe individually addressed to each target. Each target can be uniquelyidentified from information provided by its identification unit. Totalstation 732 has a controller 734, a wireless communication unit 736 andan identifying unit 738; total station 742 has a controller 744, awireless communication unit 746 and an identifying unit 748. Wirelesscommunication messages can be individually addressed to each totalstation. The identifying unit of each total station recognizes theidentity of a target from information provided by the identificationunit of the target.

FIG. 8 is a flow diagram 800 illustrating surveying methods inaccordance with embodiments of the invention. The diagram is in threecolumns: column 802 indicates activity of a human user, column 804indicates activity at a target such as target 500, and column 806indicates activity at a robotic total station such as robotic totalstation 600. To begin a survey measurement, a human user located at aselected target enters at 810 the identifier TS# of a robotic totalstation which is to measure the location of the selected target. Theidentifier TS# is entered using, for example, a keypad or other inputdevice of the target.

At 812, the target broadcasts a wireless communication message with atarget identifier TID and the identifier TS# of the total station whichis to make the measurement. If the target is equipped with a globalpositioning system receiver, the broadcast message optionally includesan approximate location of the target as determined by the globalpositioning system receiver. The target also emits a laser whichidentifies the target, e.g., a laser modulated in a way which indicatesthe identity of the target.

At 816, a robotic total station such as robotic total station 600receives and decodes the broadcast message. At 818, the message isinspected to determine if it is addressed to this total station. If no,at 820 the message is ignored or, optionally where the total station isequipped with a message forwarding capability, the message isre-transmitted to the total station addressed in the message. If themessage is addressed to this total station, at 822 the total stationseeks the target. If the message includes an approximate location of thetarget, the total station can use the approximate location to narrow thefield of search for the target and thus reduce the seek time. At 824 isdetermined whether a target laser has been detected by the totalstation. If no, the total station continues seeking a target at 822. Ifyes, at 826 the total station checks whether the detected laseridentifies the target as being the target which has requestedmeasurement of its location by this total station. If no, the totalstation continues seeking the requesting target at 822. If yes, at 828the total station locks on the identified target. At 830 the totalstation transmits a lock message to the target by wireless communicationor by laser communication.

At 832 the target receives and decodes the lock message. At 834 thetarget displays a lock indication. At 836 the user views the lockindication and is thereby informed that the total station is ready tomake the requested measurement of location of the target. At 838 theuser enters a command or commands for one or more measurements to bemade. At 840 the target transmits a corresponding measurement-commandmessage, via wireless communication or laser. At 842 the total stationreceives and decodes the measurement-command message. At 844 the totalstation takes the requested measurement and, optionally, stores themeasurement locally. At 846 the total station transmits one or messageswith measurement data, via wireless communication or laser. At 848 thetarget receives and decodes the measurement message or messages. At 850the target stores the received measurement data. At 852 the targetoptionally displays the received measurement data. At 854 the human useroptionally views the displayed measurement data.

In addition to the wireless communication possibilities mentioned above,the wireless communication units may be transceivers such as WIT2410radio transceivers available commercially from Cirronet of Norcross,Ga., USA. The WIT2410 radio transceivers provide wireless connectivityfor either point-to-point or multipoint applications. One of the unitsserves as a base station with which the others are registered andsynchronized. In point-to-multipoint network, the base station acts ascentral communications point and other radios of the network as remotes;remotes cannot communicate directly with each other.

Referring again to FIG. 8, at 820 a message received by the wirelesscommunication unit of a total station serving as a base station isrelayed to the wireless communication unit of a total station serving asa remote in the radio network. Whether the message must be decoded andinspected prior to being relayed is a matter of design choice; this maydepend, for example, on whether the radio network has a nativemessage-forwarding capability and whether the radios are operated intransparent mode.

Embodiments of the present invention provide survey systems and methodswhich offer advantages as compared with those known in the art. Althoughembodiments in accordance with the invention have been described herein,many changes and variations are possible within the spirit and scope ofthe invention as defined in the claims.

1. A surveying system, comprising: a. at least one target having i. aunique address for wireless communication, ii. a wireless communicationunit operable to activate a selected total station to identify andmeasure location of a chosen target, and iii. an identification unitcomprising a modulated light source for transmitting modulated lightemploying a modulation scheme for the modulated light which is unique tothe chosen target to enable identification of the chosen target by theselected total station, wherein the modulation scheme is adapted to bemodified prior to operating the wireless communication unit to activatethe selected total station to search for the chosen target, identify thechosen target and measure location of the chosen target, and b. at leastone total station activated by wireless communication to search for thechosen target, identify the chosen target and measure location of thechosen target.
 2. The system of claim 1, wherein the total station isoperable to measure location in relation to a relative reference system.3. The system of claim 1, wherein the system comprises a plurality oftargets, the light source of each target having a modulation schemeenabling unique identification of the target.
 4. The system of claim 1,wherein the system comprises a plurality of targets, the light source ofeach target having a modulation scheme enabling identification of thetarget, and wherein the modulation scheme may be set from measurement tomeasurement such as to give the light sources of targets close to eachother different modulation schemes.
 5. The system of claim 1, whereinthe identification unit comprises a satellite-positioning systemreceiver to determine an approximate location of the target, and whereinthe target is operative to communicate the approximate location toenable identification of the chosen target by the total station.
 6. Thesystem of claim 1, further comprising a memory to store measurementdata.
 7. A surveying target, comprising: i. a unique address forwireless communication, ii. a wireless communication unit operable toactivate a selected total station to identify and measure location of achosen target, and iii. an identification unit comprising a modulatedlight source for transmitting modulated light employing a modulationscheme for the modulated light which is unique to the chosen target toenable identification of the chosen target by the selected totalstation, wherein the modulation scheme is adapted to be modified priorto operating the wireless communication unit to activate a selectedtotal station to search for the target, identify the target and measurelocation of the target.
 8. The target of claim 7, wherein theidentification unit comprises a light source.
 9. The target of claim 8,wherein the light source has a modulation scheme enabling uniqueidentification of the target.
 10. The target of claim 8, wherein thelight source has a modulation scheme enabling identification of thetarget, and wherein the modulation scheme may be set from measurement tomeasurement such as to give the light source of the target a modulationscheme different from a modulation scheme of a nearby target.
 11. Thetarget of claim 7, wherein the identification unit comprises asatellite-positioning system receiver to determine an approximatelocation of the target, and wherein the target is operative tocommunicate the approximate location to enable identification of thechosen target by the total station.
 12. A method of surveying with atleast one total station positioned and aligned in a coordinate system,comprising: a. Placing a target at a location to be measured, the targethaving: a unique address for wireless communication, a wirelesscommunication unit operable to activate a selected total station tosearch for the target, identify the target and measure location of thetarget, and an identification unit comprising a modulated light sourceenabling identification of the chosen target by the selected totalstation, b. Transmitting modulated light from the identification unitemploying a modulation scheme for the modulated light which is unique tothe target to enable identification of the target by the selected totalstation, c. Modifying the modulation scheme prior to operating thewireless communication unit to activate a selected total station tosearch for the target, identify the target and measure location of thetarget, and d. Operating the wireless communication unit to activate aselected total station to search for the target, identify the target andmeasure location of the target.
 13. The method of claim 12, furthercomprising: transmitting data representing a measured location of thetarget from the selected total station by wireless communication forstorage in a memory remote from the selected total station.
 14. Themethod of claim 12, wherein the identification unit comprises a lightsource, the method further comprising: transmitting light from theidentification unit to enable identification of the target by theselected total station.
 15. The method of claim 12, wherein theidentification unit comprises a satellite-positioning system receiver todetermine an approximate location of the target, and wherein operatingthe wireless communication unit to activate a selected total station tosearch for the target, identify the target and measure location of thetarget comprises communicating the approximate location to enableidentification of the chosen target by the total station.